Differences between version 11 and predecessor to the previous major change of RAID.
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| Newer page: | version 11 | Last edited on Wednesday, July 13, 2005 1:32:10 pm | by DanielLawson | Revert |
| Older page: | version 9 | Last edited on Monday, May 30, 2005 1:01:29 am | by PhilMurray | Revert |
@@ -1,7 +1,9 @@
[Acronym] for __R__edundant __A__rray (of) __I__nexpensive __D__isks.
The idea behind [RAID] is having an array of disks (usually inexpensive, although that doesn't stop people buying expensive disks for their RAID array) which are all put together to form one logical disk. There are different types of [RAID] (as listed below) which all have various advantages (and disadvantages)
+
+See RaidOnLinux for some specific notes about RAID under linux.
!![RAID] 0: Striping
RAID 0 technically isn't [RAID]: It provides no redundancy or fault tolerance.
@@ -104,10 +106,13 @@
* Lots of wasted disk space
* If two disks on opposing arrays die, you lose the entire array, where 1+0 would require two disks in the same position to die before you lose the array which is far less probable.
http://www.raidarray.eu.com/raid0+1.html
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+Visual explaination of various RAID setups:
+[http://fun.sdinet.de/pics/raid.jpg]
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One suggested way of calculating the Stripe size for RAID systems that are doing a lot of random I/O (machines that are serving multiple users, eg email, compute servers etc) is to figure out the maximum throughput you can get through your disks (including controllers, PCI bus bandwidth etc). Then plug it into this formula:
stripesize = throughput / (drives * RPM/60)
then round down the stripesize to the nearest multiple of your filesystem cluster size (usually 4k).
Suggestions for the improvement of the estimation of optimal stripe size is solicited.
